feat: add and improve hints

src/App.css

@@ -1,5 +1,5 @@
 body {
-  background-color: ghostwhite;
+  /* background-color: ghostwhite; */
   color: black;
   overflow-wrap: anywhere;
 }
@@ -15,6 +15,15 @@ body {
   color: #444;
 }
 
+.hint {
+  position: absolute;
+  top: auto;
+  left: 4px;
+  bottom: auto;
+  right: 4px;
+  z-index: -1;
+}
+
 h1,
 h2 {
   margin-top: 0px;
@@ -38,6 +47,7 @@ h2 {
 }
 
 .box {
+  position: relative;
   min-width: 30%;
   max-width: 10vw;
   padding: 4px;
@@ -47,9 +57,9 @@ h2 {
 }
 
 .user {
-  max-width: 80vw;
-  width: 80%;
-  margin: auto;
+  max-width: 400px;
+  min-width: 200px;
+  margin: 4px auto;
   .item {
     font-weight: bold;
     border-style: solid;